La-Zn substituted hexagonal Sr ferrite thin films for high density magnetic recording

La-Zn substituted M type Sr-ferrite thin films were prepared by conventional rf diode sputtering. The crystallography, surface morphology, magnetic properties, and their temperature dependence were investigated by x-ray diffractometry, atomic force microscopy, and vibrating sample magnetometry. La-Zn substitution reduces the grain growth rate, so that it was possible to obtain fine grains with mean grain size about 12 nmx12 nm. Suitable amount of La-Zn substitution increases the saturation magnetization M-s of the films without changing the magnetocrystalline anisotropy of the material. As a result, the coercivity H-c increases with the increase of the La-Zn substitution. La-Zn substitution also reduces the values of dH(c)/dT of the films in the vicinity of room temperature. (C) 2000 American Institute of Physics. [S0021-8979(00)05905-3].